You can still do it with three levels of rogue. Although you can only pump skill points each level into the skills available to you by the class level you're taking (i.e., when you take a level as a rogue, you can't put any skill points into scry), your max ranks in a skill are determined by your character level, not your class level.
Go rogue at first level, and take four ranks of decipher script. That's your maximum.
Take your next five levels as wizard.
At seventh level, take a level as rogue: now your max ranks in any skill that is a "class skill" for you (i.e., any skill that has EVER been a class skill for any class you've taken) is 10. Pump three of your skill points into rogue, and you're golden.
Eighth level gets you your +2d6 Sneak attack; ninth level starts you on the path to trickery.
My next character, already statted out and ready for the first Tuesday in September, is a Rog1/Necromancer3 well on her way to Arcane Trickster classhood. I'm looking forward to it a lot.
Daniel